IPad Pro with Microsoft Programs

I am having so many problems using Excel and Microsoft Word on my iPad Pro. It seems to get worse as time goes on. I need to be able to open excel sheets and documents from Dropbox. Now, it either will not open at all or it will not upload to Dropbox or it will say someone else has the file open. I have shut down my ipad and restarted the programs, but it is a persistent problem. Some of the files are large, but some are not.